title: Regulatory properties and interaction of the C- and N-terminal domains of BetP, an osmoregulated betaine transporter from Corynebacterium glutamicum.
abstract: The glycine betaine carrier BetP from Corynebacterium glutamicum responds to changes in external osmolality by regulation of its transport activity, and the C-terminal domain was previously identified to be involved in this process. Here we investigate the structural requirements of the C-terminal domain for osmoregulation as well as interacting domains that are relevant for intramolecular signal transduction in response to osmotic stress. For this purpose, we applied a proline scanning approach and amino acid replacements other than proline in selected positions. To analyze the impact of the surrounding membrane, BetP mutants were studied in both C. glutamicum and Escherichia coli, which strongly differ in their phospholipid composition. A region of approximately 25 amino acid residues within the C-terminal domain with a high propensity for alpha-helical structure was found to be essential in terms of its conformational properties for osmodependent regulation. The size of this region was larger in E. coli membranes than in the highly negatively charged C. glutamicum membranes. As a novel aspect of BetP regulation, interaction of the C-terminal domain with one of the cytoplasmic loops as well as with the N-terminal domain was shown to be involved in osmosensing and/or osmoregulation. These results support a functional model of BetP activation that involves the C-terminal domain shifting from interaction with the membrane to interaction with intramolecular domains in response to osmotic stress.
authors.affiliation: Institute of Biochemistry, University of Cologne, 50674 Cologne, Germany, Institute of Biochemistry, University of Frankfurt, 60438 Frankfurt, Germany.
authors.forename: Vera
authors.initials: V
authors.lastname: Ott
authors.forename: Joachim
authors.initials: J
authors.lastname: Koch
authors.forename: Kira
authors.initials: K
authors.lastname: Späte
authors.forename: Susanne
authors.initials: S
authors.lastname: Morbach
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krämer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001622:Betaine / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation / Q000502:physiology; D009995:Osmosis / Q000502:physiology; D009997:Osmotic Pressure / Q000502:physiology; D017433:Protein Structure, Secondary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D027981:Symporters
chemical_list: D001426:Bacterial Proteins; C101652:BetP protein, Corynebacterium glutamicum; D002352:Carrier Proteins; D011994:Recombinant Proteins; D027981:Symporters; D001622:Betaine